Urinary tract infection (UTI) is one of the most common bacterial infections encountered by humans. Uropathogenic Escherichia coli (UPEC), Klebsiella pneumoniae and Proteus mirabilis are the predominant etiological agents of UTI. Women, children, and the elderly are highly susceptible to UTI. Meteoric increase in antibiotic resistance rates in uropathogens raises an urgent need for the development of novel strategies to manage UTI. Our work has demonstrated that copper is mobilized to urine as a host response during clinical UTI in patients and is involved in protection against UTI in the mouse model. Our findings and reports of fatal complications of UTI in patients with Menkes disease (who cannot absorb dietary copper), highlight a novel biological role for copper in the protection against UTI. Our long-term research goal is to define the molecular and cellular features of host-pathogen interaction during UTI to identify targets for therapeutic development. The major objective of this proposal is to determine the impact of endogenous and increased urinary copper on bacterial colonization during UTI. Based on our published and preliminary data, we hypothesize that host- derived copper is involved in protection against uropathogen colonization and increasing urinary copper content will promote bacterial clearance during UTI. The rationale for this study is that understanding the protective role of copper on bacterial colonization during UTI is critical to develop therapeutics that bolster this innate response to resolve UTI. Utilizing a mouse model of UTI, clinical isolates of UPEC, K. pneumoniae and P. mirabilis, and isogenic bacterial mutants lacking copper-efflux pumps, we will test our central hypothesis by pursuing the following Specific Aims: 1) Determine the impact of endogenous, host-derived copper on deterring bacterial colonization during UTI; and 2) Determine the effect of increased urinary copper level on bacterial clearance from the urinary tract. The expected outcome of this study is to understand the impact of endogenous copper on clearance of clinically significant uropathogens from the urinary tract during UTI. Increased urinary copper content is anticipated to promote bacterial clearance in the mouse model of UTI. The substantial positive impact of this study will be elucidating the role of an innate host defense effector in protection against UTI by major uropathogens. The proposed research is significant because our findings are anticipated to break new ground to develop novel interventions against UTI. Our approach is innovative because we seek to bolster a host effector that is amenable to modulation by dietary and pharmacological intervention to promote resolution of UTI. In summary, the proposed study is expected to confer a significant public health benefit against UTI, a ubiquitous and profoundly painful infectious disease affecting millions of people.